The present invention relates generally to fabrics receptive to printing or dyeing, and, more particularly, to a synthetic-rich fabric with an improved propensity for dye penetration, dye fixation, and a soft hand.
Dyeing has been a part of the finishing process for textiles for thousands of years. For both aesthetic and practical reasons, fabrics and apparel crafted therefrom have been subjected to bleaching and coloration processes.
There are a number of dyeing processes currently in practice, depending upon the particular yarns forming the knitted, woven, or non-woven fabrics. For instance, the natural and man-made fibers and filaments have differing affinities for dyestuffs. Further, fabrics may be either piece dyed, tie dyed, or printed. Printing types include conventional roller printing, flat screen, rotary screen printing, digital printing, and heat transfer (sublimation) printing.
As a general rule, the printing of fabrics made from man-made (synthetic) fibers or filaments has been problematic. Synthetic yarns tend to be hydrophobic and therefore hard to print with pigments, as pigments do not penetrate the yarn, but rather are affixed to the surface of the fabric. Synthetic fabrics such as polyester, nylon, and others are dyestuff-specific and may not accept all categories of dyestuffs. Heat transfer printing with disperse dyes has been found acceptable for synthetics and produces a well-defined pattern on the face of the fabric; however, this type of printing requires that disperse dyes be first applied to a paper substrate and then heat transferred to a fabric surface. While the outer printed surface has a satisfactory appearance and sharpness of lines, the disperse dyes do not completely penetrate the yarns forming the fabric, resulting in an undyed inner surface and an unacceptable dyed appearance when the fabric is stretched, due to lack of dye penetration between yarns.
Disperse dyes may be applied directly to a fabric; however, heretofore the resulting product has not had as soft a hand, the level of crocking, or as good a level of colorfastness as disperse dyes applied by the heat transfer method. Further, the disperse dyes have not been compatible with conventional softeners. This is the problem addressed by the present invention; that is, how to obtain a better dye result with disperse dyes applied directly to synthetics.
The end use of an item of apparel dictates the combination of yarn, fabric construction (woven, knitted, etc.), finishing, and dyeing that goes into the item. For example, important characteristics of many items of apparel include softness, firmness, fineness, or other qualities perceived by touch, and the ability of the material to disperse or spread moisture, or wicking. Softness is often the desired quality in apparel. To achieve this quality, particularly in synthetic fabrics, chemical finishes such as softeners are used. Unfortunately, conventional softeners have typically been hydrophobic, that is, lacking an affinity to absorb water, or dyes. This has been particularly true where disperse dyes have been used. For many items of outerwear, particularly work clothing, a high level of wicking is desirable for the comfort of the wearer. Wicking agents are applied to synthetic fabrics to achieve this result.
The present invention is directed to a synthetic-rich fabric and apparel formed therefrom that has improved dye penetration, colorfastness, and a soft hand not heretofore known in synthetic-rich fabrics where the dye is applied directly to the fabric.
In the preferred embodiment of the present invention, a knitted fabric is formed from 100 percent polyester yarn, although other synthetic-rich yarns are equally suitable. As used herein, xe2x80x9csynthetic-richxe2x80x9d means that at least 51% of the yarn is polyester or other suitable synthetic yarns and 49% or less of the yarn is natural.
Any conventional fabric construction may be printed with the present invention, but the preferred embodiment is a knit construction. The knit construction may be single knit, double kit, etc. and there is no limitation on the type of knitting machine that may be used to form the initial knitted fabric. Further, yarns sizes are not critical to the present invention, but spun polyester in counts of 10/1 to 40/1 have been found most suitable. Alternatively, continuous filaments could be used to form yarn constructions having composite deniers between about 40 and 300.
The knitted fabric is initially chemically treated with a wicking agent and heat set. In addition to being hydrophilic, which aids substantially in the penetration of directly applied disperse dyes, the wicking agent used herein produces a secondary benefit of creating some softening in the fabric. Additionally, a hydrophilic softener may be applied to the knitted fabric. Heretofore, softeners have not been used for printed synthetic fabrics because of their hydrophobic characteristics which impede dye fixation, particularly with disperse dyes.
Once chemically treated with the wicking agent (and hydrophilic softener as desired), the treated fabric is ready for the printing process. In the preferred embodiment, rotary screen printing is used, but other printing processes such as immersion and continuous dyeing, flat screen, conventional rollers, or digital could also be used. With the rotary screen printing machine, one or more disperse dyes are used to obtain the desired color pattern. Disperse dyes are a class of water-soluble dyes usually applied from aqueous solutions and known for dyeing synthetic fibers, although only heat transfer printing has yielded satisfactory results. In the present invention, the dyestuffs arc suspended using a commercially available concentrate and applied directly to the fabric by the rotating screens.
Following printing, the printed fabric is subjected to a fixation process using a conventional heat setting machine. The printed fabric is passed through a tenter frame where it is stretched to the desired width with steam and then fixed through propane gas heating at about 350 degrees Fahrenheit for between about 1.5 and 2 minutes. Alternatively, the dye fixation could be accomplished using infrared heating at the same temperature and for the same amount of time.
Once the printed fabric has been heat set, the final product is complete and ready for packaging. It has been found that the combination of disperse dyes and a wicking agent, when applied to a 100 percent knitted polyester fabric, produces unexpected results in the final fabric. That is, the final fabric exhibits both a dry and wet crock of at least 4.0. Additionally, the colorfastness of the finished dyed fabric is excellent, measuring 4 when subjected to the American Association of Textile Chemists and Colorists (AATCC) Test Method 61-1996, xe2x80x9cColorfastness to Laundering, Home and Commercial: Acceleratedxe2x80x9d, which measures colorfastness on a scale of 1 to 5. The final fabric also has a soft hand. As used herein, xe2x80x9chandxe2x80x9d refers to that characteristic widely known in the textile industry as the tactile quality of a fabric; e.g., softness, firmness, elasticity, fineness, resiliency, and other qualities perceived by touch. Thus, the final fabric of the present invention exhibits a soft, as opposed to a rough or stiff, hand.
These and other aspects of the present invention will become apparent to those skilled in the art after a reading of the following description of the preferred embodiment when considered with the drawings.